<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;height: 50px;background-color: red;
      position: absolute;
      z-index: 1;
    }
    #d2{
      width: 50px;height: 100px;background-color: green;
      position: absolute;
      /*当元素为非static定位时,可能会出现层叠显示的问题,通过z-index设置显示层级
      设置z轴的位置 值越大越靠前,如果值相同则 后添加的显示在上面*/
      z-index: 2;
    }
  </style>
</head>
<body>
<div id="d1"></div>
<div id="d2"></div>

</body>
</html>